class Queue:
  """ 使用列表模拟列表 """

  def __init__(self):
    self.items = []

  def isEmpty(self) -> bool:
    return self.items == []

  def enqueue(self, item):
    self.items.insert(0, item)

  def dequeue(self):
    return self.items.pop()

  def size(self) -> int:
    return len(self.items)
